I just bought a 1000w generator from Amazon for $115. This no Honda 1000. But, it also is not $799.

The run rating is 900w. I ran a 900w space heater for 2 1/2 hours yesterday with no problems. They say the National Park Service accepts it. I would not want it in the my campsite or next to me. It will run many tools. It will also run my beer refrigerator during a power outage. It's not big enough for the Bartender. It won't run a water heater or a 2 burner hotplate.

I used mine on the beach to charge the battery, the boat was an open boat. I don't see how a decent carbon monoxide detector would cost just as much as the generator. I just installed a new one of excellent quality near my home water heater after replacement, must of run somewhere around $20.

I would not want to run one on a cabin or cuddy boat while underway, but don't see any reason one could not be lugged along safely for recharging a battery on the shore, providing the boat could be beached. This generator, the Honda EU1000 (excellent quality!), or similar clones are very quiet and do not use much fuel. Great for charging batteries or similar.

Generator weight is approximately 37 lbs and holds 1.1 gallons of gasoline, which at 6 lbs per gallon gives one a total weight of 43.6 lbs, much less than a spare battery...

I plan on using mine with the Minuet I am building. For the record, quite a few folks who "live aboard" use these (usually a bit larger, upwards of 3.5 kw) to run air conditioning units temporarily fitted in the companionway while in tropical locations, such as Florida...

A decent marine battery (24, 27, 29, or 31 series) coupled with a 180 solar watt panel which should provide a nominal 7.5 amperes (at 50% output), taking some load off the battery, could give one a reasonable run time for onboard electronics upwards of 20 hours with one battery. Upon beaching or mooring, a quiet generator could be used to recharge the battery for the next day.

Of course, if you are cruising overnight, something else would be necessary, such as wind (quite a few of the models I have found put out a very generous amperage, provided you have wind, of course).

Although much of this is new to me, it seems if you are cruising offshore in the evening, it is very likely you are in a larger boat with an inboard diesel.

One can purchase or fab a bracket to add a second alternator to a Yanmar diesel, and the amperage is limited by the load on the shaft (too much of a load causing premature bearing failure), typically a serpentine or double belt option is used. In my research, the maximum load which can be placed for this setup is 190 amps. If you have the high capacity alternator (125 amperes), then you have a budget of 315 amperes at full load, or 3,780 watts, which would be more than enough to run the onboard electronics, radar, A/C (if installed), etc. This would come at a cost of a little over 5 hp, assuming 100% efficiency (which we don't see in the real world, of course).

If the max horsepower spec'd for an inboard is 35 hp, then upsizing to a 40 hp diesel would compensate...

I'm not sure that marine detectors are needed on a small cuddy cabin with the generator separated from the cabin. Marine detectors can be linked to several other detectors. I think that is over kill in a 12 foot cabin. They can also be set up to turn off the generator, if you have that setup. CO is lighter than air and goes up. Mount the detector high in the cabin. If you cook with propane, you may need both a CO monitor up high and a propane detector mounted down low. Propane is heavier than air and goes down.